NGRI: Earth Test To Determine Pollution

April 28, 2008
By Syed Akbar
Hyderabad: The National Geophysical Research Institute has come out with a unique geochemical baseline mapping system which will serve as a watchdog for polluters.
The pilot project is being implemented in the backward Medak district of Andhra Pradesh. According to NGRI scientist Dantu Sujatha, the experience gained from the regional geochemical baseline mapping in Medak district will be useful for efficient planning and promoting the methodology for developing low cost environmental baseline data in other places.
Geochemical baseline is the concentration of a given chemical parameter in a given sample of geologic material at a given point in time. This is in contrast to geochemical background, which is the natural abundance of an element in a particular material with no human interference The concept of geochemical baseline mapping gained importance during 1986 after the explosion at Chernobyl nuclear power plant. Geochemical baselines are very important in environmental legislation, which prescribes limits for heavy metals in contaminated land and other surface materials as defined by environmental authorities, she said.
"While it does not appear that we are going to neutralise the threat of heavy metal toxicity in our communities nor decrease our utilisation of the many commercial goods that they help produce, we can take steps to understand this threat and put into action policies of prevention and treatment that may help to lessen the negative impact that these agents have on human health," Sujatha told this correspondent.
The increase/decrease in trace elements in soils is an important factor in the development of urban and agricultural areas as these trace elements may adversely affect the soil, environment, agricultural production or crop quality and ultimately ground water quality.
The Medak project is funded by the Department of Science and Technology. The aim of the study is not only to provide reliable analytical data to display large patterns of geochemical signatures on the regional scale, but also to investigate the different factors influencing these patterns, notably bedrock geology, climate and human influences.
Distribution patterns reflect the geological and climatic variation, differences in topography, age of the soil, land use changes, agricultural practices and pollution. The resulting database and maps would help the policy makers to decide the future industrial areas, land use, agriculture
activities etc.
The entire study area (9699 km2) is divided into 10/10 km grid and from each such grid; soil sampling is carried out based on the knowledge acquired from geology, morphology, vegetation, soil and hydrology maps.
The top layer usually comprised the plough layer which is vertically homogenised by agricultural practice. It is assumed that human activity primarily influenced this soil layer. The subsoil samples are assumed to represent the pristine soil composition.
Soil samples after processing are analysed for 10 major heavy and 14 trace elements.
A detailed geochemical database and preparation of high-resolution easy-to-read maps illustrates regional patterns. The visualisation of the geochemical maps aid in the integration of geochemistry with the regional geology. These maps can indicate areas where there is the potential for trace element deficiency or toxicity, enabling expensive veterinary or medical investigations to be better targeted.